Casing for push-pull cable assembly



Jan. 10, 1956 J. F. MORSE CASING FOR PUSH-PULL CABLE ASSEMBLY 2 Sheets-Sheet 1 Filed Oct. 6, 1950 United States Patent 2,730,134 I CASING FOR PUSH-PULL CABLE ASSEMBLY John F. Morse, Hudson, Ohio Application October 6, 1950, Serial No. 188,809

2 Claims. (Cl. 138-57) The present invention relates to what are known in art as push-pull cables, in which a flexible core member, usually in the form of a cable, is employed to transmit mechanical motion in either direction. This type of mechanism is well known in the art and it is the purpose of the present invention to improve upon the construction and design of the outer casing member through which the core member slides.

The usual existing forms of easing have a number of objections which are overcome by the present invention. The type of casing shown and described herein is of a design which is adaptable for installation at the point of use. This enables the user to purchase the casing in long lengths, which are cut on the job to fit the requirements thereof. The new form of easing also adapts itself to the attachment of end fittings either of the permanently swaged on type or of the detachable type.

One of the advantages of the new form of casing is its ability to withstand high compression or tension loads without buckling or stretching. In the operation of the core member of the push-pull cable assembly the force which is applied to the end of the core member to shift it in the casing is transmitted to the casing, but in the opposite direction. The casing of the present invention is constructed so that it will resist much heavier forces than is possible with ordinary types of casings, hence much greater loads may be applied to the core member.

The casing is also designed so that it will withstand high compressive loads which would crush casings made in accordance with prior art practices. Should heavy tools or machinery bump against or be placed on the casing, it will not crush. The casing is also designed to resist kinking or excessive bending at localized points, but it has sufficient flexibility so that it may be bent around corners or over beams, or other obstacles when installed.

The casing is also water and oil tight and will remain so under severe conditions of wear and rough usage, and will resist abrasion or other forces which would injure older forms of casings.

One of the main advantages of the invention resides in the fact that the construction of the casing permits a substantial reduction in the clearance between the inner wall of the casing and the outer surface of the slidable core member. Reduction in clearance between the casing and the core member reduces the opportunity for bending or buckling of the core member. In older forms of casings it has been necessary to provide an excessive amount of clearance between the core and the interior of the casing because of the possibility of the casing becoming deformed, for various reasons. The present form of casing also provides a yielding layer between the inner and outer walls of the casing, which will absorb compression loads placed upon the casing and thus the clearance between the core and the interior of the casing may be substantially reduced.

The casing shown and described herein has a degree of inherent springiness which causes it to lie in a straight line when free to do so, rather than tending to curl or bend, as is the case with older types of casings. This feature is especially valuable when the core member has a like tendency to lie in a straight line because it reduces the frictional drag between the core and the casing. The form of casing shown herein has the further advantage that it will not tend to unravel when cut, thus eliminating any necessity for holding the wires which constitute the casing at the points of cutting to prevent untwisting of the casing.

One of the objects of the invention is to provide a novel connection between the casing end fitting and the mechanism by which the core is operated in the casing. The slidable core member is operated by a pivoted crank lever acting through telescopic guides which impose a direct thrust on the core member, one of the guides being secured to the casing end fitting. Ordinarily, the flexibility of the casing is relied upon to allow for the swinging movement of the crank, but where the loads imposed on the core member are extremely heavy it is desirable to provide for swiveling the core operating mechanism in the casing end fitting.

The invention is disclosed in sufficient detail so that the principles and operation thereof will be understood, but it is not intended that the invention be limited to the details as modifications and variations may be made within the scope of the invention as expressed in the appended claims.

In the drawings:

Fig. l is a side elevation of one end of a push-pull cable assembly comprising the improved casing of the present invention. In this embodiment of the invention, a pivoted operating lever is attached to the core and the casing is extended beyond the clamping means therefor so as to allow for the rocking movement of the lever by the bending of the casing.

Fig. 2 is a side elevation of an alternative type of mounting in which the rocking movement of the operating lever is permitted by a ball and socket connection between the operating lever and the fitting on the end of the casing.

Fig. 3 is a longitudinal section through the casing and the end fitting shown in Fig. 2.

Fig. 4 is an enlarged section through one side of the casing on the line 4-4 of Fig. 3.

Fig. 5 is an enlarged section through one side of the casing at the point of attachment of the end fitting, the location of this view being indicated by the line 5-5 of Fig. 3.

In the drawings, the movable core member is indicated generally by the numeral 1. This core member may be any of the standard forms of cores, but it is preferred to employ that type of core member which consists of a central cable usually composed of nineteen strands of wire spirally wrapped to form an inner cable 2 and an outer covering consisting of a fiat metal ribbon 3 spirally wrapped about the inner cable and compressed thereon, the core assembly constituting an armored strand which is common in the art. This type of core member is preferred because of its high efiiciency and also because it has a smooth outer surface and tends to lie in a straight line. Hence it does not create as much friction with the interior of the casing as other types of core members.

The outer casing is indicated as a whole by the numeral 5, the details of which will be described later. In making the installation the user cuts ofi a length of the casing sufficient for the requirements and secures it in location by any suitable means, an ordinary clip for this purpose being shown at 6 in Fig. 1. The user then cuts oif a length of the inner core member suflicient so that a substantial portion of the core member will project from either end of the casing for attachment of the end fittings for the core.

While many types of core end fittings may be used, the preferred form is that shown in the drawings. The core member 1 is extended into an end fitting which is a bar of metal having a bore 11 to receive the core member, which is securely clamped to the fitting by screws 12 threaded into the fitting and holding the core by deforming it as shown in Fig. 2. This preferred means of securing the core to its. end fitting is covered in the prior application of this applicant, Serial No. 185,420, filed September 18, 1950,. now Patent No. 2,643,146.

The end fitting 10 is pivotally connected at 14 to the operating member here shown as a pivoted lever or crank arm 15. Secured in a socket in the outer end of the fitting 10 is a guiding member in the form of a tube 16 which surrounds the core member and is telescopically received in a sleeve 18 attached to the end of the casing by an end fitting. By this means any movement of the operating lever imparts a direct thrust to the core member.

The end fitting for the casing is indicated as a whole in both Figs. 1 and 2 by the numeral 20. The means by which this end fitting is securedrto the sleeve is the same in both embodiments of the invention and will be later described- The means by which the sleeve 18 is attached to this end fitting in. the form shown in Fig. 1 consists in providing a socket 22 in the member 21 of the end fitting. The end of the sleeve 18 is force fitted and brazed in the socket so that the sleeve is rigid with the end fitting. In this embodiment of the invention the necessary flexibility for operating the lever 15 and providing for free sliding movement of the tube 16 in the sleeve 18 is provided for by the. end of the flexible casing 5 which is extended for a sufficient distance beyond the nearest clip or holder 6 to allow for the movement of the. operating lever.

This method of assembling. is usually employed on light duty cable assemblies where the loads exerted by the operation of. the lever 15 are not excessive. However, it is not well suited for assemblies in which the loads transmitted by the core member are extreme and for this reason the modification shown in Fig. 2 has been devised.

In the form of the invention shown in Fig. 2, the member of the casing end fitting corresponding to the part 21 in Fig. 1 is given the reference numeral 25. This member is provided with a threaded extension 26 in. which is formed. a spherical socket 27. The guidingsleevc 18a in this case is provided with a mating spherical head 28 which fits in the socket 27 and is apertured at 29 providing for the angular movement of the core end fitting and the casing on the rocking of the lever 15. The end of the extension 26 is peened or spun over the head 28 to hold the elements together.

In the form shown in Fig. 2, the casing end fitting is held in position by a bracket 32, one arm of which is apertured to fit over the threaded outer end of the member and is held in position against a flange 33 by the nut 34 on. the extension. The other arm of the bracket is adapted to be fastened in location by bolts or screws 36, which give a rigid support for the end of the casing. The method of securing the end of the casing in position has advantages where the loads exerted on. the core are extremely heavy and also where there is little room to mount the operating member.

Referring now to the details of the casing design: This is composed of an inner member made of a substantially rectangular wire 36 which is wrapped in a tight coil or helix, the inner diameter of which is slightly greater than the outer diameter of the core member 1. As explained above, one of the advantages of the invention is that it enables the clearance between the core and the casing to be reduced substantially over old forms of cable assemblies, thus reducing any tendency of the core to buckle or bendv in the casing, under heavy loads and giving much smoother operation. In the present invention the clearance need be only sufficient to provide a free sliding bearing between core and casing, with a small amount of lubricant.

It will be noted that the inner and outer surfaces of the wire 36 are flat but that the edges thereof are formed on an arc, which permits a certain amount of flexing in the casing necessary to permit its installation. It will also be noted that the common tangent of the curved edges at each contact point is perpendicular to the axis of the casing to permit the casing to bend without relative transverse displacement of the turns. As. a result the inner surface of the casing is maintained at constant diameter during bending.

Placed about the inner lining formed by the spiral wire is a sheath of an oil resistant rubber or rubber-like material 33 which is ordinarily extruded and cured over the coil 36. While rubber is normally used, rubber substitutes, plastics, or other resilient materials having waterproofing and yielding properties comparable to rubber may be employed. This sheath is of substantial thickness and not only gives the oil and waterproof protection to the interior of the casing but also serves as a cushion to protect the inner wire helix from crushing.

Over the sheath 38 is applied the outer spiral wire wrapping which is given the reference numeral 40. This is composed of a plurality of steel wires wrapped in long spirals, with the turns thereof closely spaced but not in actual contact, as shown inFig. 4, and with the spiral on the opposite hand from the spiral of the inner wire 36. The wires 46 are preformed before being wrapped about the outside of the casing, by which is meant that the wires are formed in substantially the condition in which they will lie in the finished product before wrapping them about the sheath. By preforming the wires 40 in the manner described, the casing does not exhibit any tendency to twist or writhe, and hence it will remain in a straight line when no bending force is applied to the casing, but the casing may be flexed when it is installed. The preforming of the wires also eliminates any tendency of the wires to untwist or ravelwhen the casing is cut. When the wires 40 are applied over the intermediate rubber sheath, the wires will embed themselves to a limited extent in the rubber, as shown in Fig. 4.

The casing which has been described is ideally suited for attachment of the casing end fittings as will be understood from a further description of this element of the assembly. The outer spiral wire gives an exceedingly durable and abrasive and wear resisting outer covering for the casing and also provides a high tensile strength when the push-pull cable is Working under heavy compression loads. The heavy inner coil of wire 36 provides the desirable compressive strength when the push-pull cable is working under heavy tensile loads. Both inner and outer coils, together with the intermediate cushion 33 prevent the casing from crushing under heavy external loads, and the combination of the inner and outer coils all tends to resist excessive local bends and to maintain an even and fairly large radius where bends occur, all of which contributes to the smooth operation of the inner cable in its movements to and fro in the casing.

Referring now to the casing end fitting: In the forms of the invention shown in both Figs. 1 and 2, the member 21 or 25 is the male. member of a threaded coupling by which the operating elements for the core are securely attached to the end of the casing. The female member in each case is indicated by the numeral and both elements of the coupling are provided with flattened areas by which they may be rotated relatively to one another in making or detaching the coupling.

The male member is provided with a threaded extension 46, which is received within the internally threaded extension 47 on the female members, and the inner end of the male member is formed with the cone shaped socket 48. At the base of the threads on the female member of the coupling or joint is a shoulder 50 and in the space between the two elements of the coupling is the clamping ring 52, one side of which bears against the shoulder. The other side of the ring is formed with a reduced skirt or extension 54, which fits into the conical socket on the male member of the coupling and is preferably split so that as the two coupling members are brought together the skirt will be contracted by the coneshaped socket and will bite into the outer surfaces of the wires 40. The edge of the skirt should be sharpened so as to dig into the several wires as shown in Fig. 3. In this view one of the lowermost wires 40a is shown in extension so as to illustrate this operation; a true section at this point will show the wires as elongated ovals as they appear in the upper portion of the view.

The action of the coupling is illustrated by comparing Figs. 4 and 5. Tightening of the two elements of the coupling causes the edge of the skirt to dig into the wires. It also crowds the wires 40 together and causes the rubber of the sheath 38 to flow into the interstices between the wires. This makes an extremely secure anchorage for the casing end fitting.

It will be noted, however, that the tightening of the coupling cannot reduce the innermost diameter of the casing due to the fact that the wires 36 are in a tight coil and also due to the fact that the rubber cushion between the inner and outer coils will permit a contraction of the inner diameter of the outer coil without crushing of the inner coil.

It will be seen that the assembly shown and described herein is one which may be easily cut and assembled on location, which reduces the cost of push-pull cable installation. The casing is ideally adapted for the attachment of a casing and fitting and particularly for that shown herein. There is no reduction in the inner diameter of the casing so that it is possible to make a push-pull cable installation in which there is the minimum amount of clearance between the cable and the casing, resulting in the minimum amount of backlash. The casing assembly is unusually rugged and adapted to withstand all loads placed upon it. It is practically indestructible and pro tects the interior of the casing from oil and water.

Where the term rubber or rubber-like is used in the claims, it is intended to cover all types of rubber or rubber-like or composite material which gives the desired yielding and waterproofing characteristics to the assembly. While the high efliciency type of core member is preferred, other core elements may be employed and while other types of couplings may be substituted for that shown, the form shown is best adapted for use with the casing which has been described.

What is claimed is:

1. A flexible casing for the core of a push-pull cable assembly having an inner reinforcing member to withstand high compression loads without deformation and an outer reinforcing member to withstand high tensile loads without elongating, said inner reinforcing member consisting of a flat wire ribbon tightly wrapped in a helix with the edges of the turns of the ribbon in contact, the said edges being rounded with the common tangent at each contact perpendicular to the axis of the casing to permit the casing to bend without relative transverse displacement of the turns and the inner surface of the neiix forming a constant diameter sliding bearing for the core, a sheath of rubber surrounding the inner reinforcing member, said outer reinforcing member consisting of a plurality of wires spirally wrapped about the casing in relatively long spirals and having a permanent set in spiral form, said outer wires being partially embedded in the rubber sheath, the wires forming the outer memher being spaced apart to permit them to be further further embedded in the rubber sheath.

2. A flexible casing for the core of a push-pull cable assembly having an inner reinforcing member to withstand high compressive loads without deformation and an outer reinforcing member to withstand high tensile loads without elongating, said inner reinforcing member consisting of a flattened wire ribbon tightly wrapped in a helix with the edges of the turns of the ribbon in contact, the contacting edges being rounded with the common tangent at each contact perpendicular to the axis of the casing to permit the casing to be bent without relative transverse displacement of the turns and the inner surface of the helix forming a constant diameter sliding bearing for the core, said outer reinforcing member consisting of a plurality of wires spirally wrapped about the casing in relatively long spirals and having a permanent set in the spiral form, and a sheath of rubber interposed between the two said reinforcing members.

References Cited in the file of this patent UNITED STATES PATENTS 753,230 Calcutt Mar. 1, 1904 1,385,821 Goodall July 26, 1921 1,520,705 Farmer Dec. 30, 1924 1,633,701 Haynes June 28, 1927 1,918,792 Arens July 18, 1933 1,993,907 Williams Mar. 12, 1935 2,225,333 Daniels Dec. 17, 1940 2,438,053 Hettings Mar. 16, 1948 2,484,815 Crawford Oct. 18, 1949 FOREIGN PATENTS 445,408 Great Britain Apr. 8, 1936 736,394 France Nov. 23, 1932 

